Clinically Significant Bone Preservation and In-Growth Around Implants Made With Zimmer's Trabecular Metal Material May Improve Long Term Biologic Implant Fixation and Simplify Revision Procedures

WARSAW, Ind., July 20 /PRNewswire-FirstCall/ -- Zimmer Holdings, Inc. (NYSE: ZMH; SWX: ZMH) today announced that data from a comparative clinical study conducted by researchers at the Mayo Clinic and the Joint Replacement Surgeons of the Indiana Research Foundation describes the low stiffness and osteoconductive properties of Zimmer's Trabecular Metal Technology. The study, published in The Journal of Arthroplasty, found significant reductions in acetabular bone loss adjacent to the Trabecular Metal device compared to the titanium component, and a significant relative increase in bone mineral density (BMD) after total hip arthroplasty (THA) using implants made with Zimmer's proprietary Trabecular Metal Technology.

Researchers followed 17 THA patients over the course of 6 to 9 years and compared bone loss around highly porous Trabecular Metal cups versus titanium cups with a similar geometry. This is the first study to quantify bone-remodeling around hip implants at an intermediate term (mean of 7.7 years) follow-up. Bone mineral density adjacent to acetabular implants was evaluated using quantitative computed tomography (QCT). The data demonstrated that stress-shielding around standard titanium cementless acetabular components continues well beyond the short-term. The study revealed that patients with Trabecular Metal monoblock cups experienced up to a 41% increase in mean BMD around certain areas of their implants, compared to a loss of up to 45% in BMD in certain areas of the control hips with titanium cups.

It is well established that a decrease in bone density may compromise the long term success of the primary surgery and may increase the difficulty and expense of revision reconstruction. Acetabular stress-shielding can also exacerbate patients' osteolytic response to bearing surface particles, potentially further reducing the bony support for the implant. The authors of the study suggest that the elasticity (low stiffness) of Trabecular Metal material may induce a transfer of stresses to the periacetabular bone that more closely replicates the normal physiologic load transfer, thereby decreasing the detrimental effects of stress-shielding by allowing the bone to respond to normal loading patterns. In this study, clinically significant bone preservation and in-growth were observed radiographically around Trabecular Metal implants. These results indicate the potential for improved long term biologic fixation with Trabecular Metal implants and could result in fewer and less complex revision procedures.